1. Field of the Invention
This invention relates to affixing pins to a ceramic substrate and more particularly to affixing pluggable pins to a ceramic substrate for use in pluggable electronic circuit package assemblies.
2. Description of the Prior Art
In the electrical arts, it is well known to affix electrical conductive pins to an insulative base member.
U.S. Pat. Nos. 1,914,651, 1,936,404, 2,292,863, 3,211,875, 3,670,294 and 4,753,602, and the publication entitled "Swaged Hollow Electrical Inlet Pin", IBM Technical Disclosure Bulletin Vol. 29 No. 2, July 1986, pp 639-640, are examples of pluggable pins affixed to an insulating base for electrical devices such as radio or vacuum tubes and electrical wire connectors. U.S. Pat. No. 4,136,259, discloses an igniting electrode for a burner in which an insulating ceramic body houses an electrically conducting metal stem.
U.S. Pat. Nos. 2,846,659, 2,990,533, 3,093,887, 3,202,755, 3,484,937, 3,494,029, and 3,601,750, Australian Patent, No. 247,745 (published 29 November, 1962), Canadian Patent, No. 891180, (issued Jan. 18, 1972), and the publication entitled "Terminal Pin Projector"--H. P. Byrnes, IBM Technical Disclosure Bulletin, Vol. 9, No. 4, September 1966, p 365, are examples of pluggable and/or non-pluggable type pins affixed to non-ceramic substrates and more particularly affixed to printed circuit boards.
U.S. Pat. Nos. 3,216,097 3,257,708, 3,489,879, 3,529,120, 3,735,466, 3,768,134, 4,082,394, 4,092,697, 4,110,904, 4,415,113, 4,598,470, and 4,631,821, and the publications entitled "Pinning Technique For Ceramic Module"--J. R. Lynch, "Brazing Contact Pins To Ceramic Substrates"--B. Martin et al, and "Low-stress Pin Insertion"--R. J. Modlo et al, IBM Technical Disclosure Bulletin,. Vol. 14, No. 1, June 1971, pp 174-175, Vol. 14, No. 9, February 1972, p 2594, and Vol. 22, No. 8B, January 1980, pp 3649-3650, are examples of of pluggable pins affixed to ceramic substrates.
In the aforementioned Patents, Nos. 1,914,651 and 1,936,404, hollow pin type contact members are affixed to a base member of porcelain, bakelite, glass or other similar material. The resultant sub-assembly is used as a component for radio or vacuum tubes. In No. 1,914,651, the individual pins have a pre-formed head flange at one end. To affix the pin to the base, the other end of the pin is inserted into an opening that extends through the base until its motion is stopped by the head. When this occurs the other end of the pin and a portion of the pin body extends outwardly from the base member. Thereafter, a circumferential bead is forged in the outwardly extended portion of the pin to affix the pin to the base member between the head and the bead. In certain of the embodiments of No. 1,936,,404, the bead is pre-formed and molded in the base or may be staked. No. 1,914,651 describes a prior art device in which after the hollow pin with a preformed shoulder is pushed into place the end of the pin is spun over to hold the pin in the opening of the base.
The pins of No. 2,292,863 have a preformed flange and the pins are affixed to a metallic header by a fusible vitreous material sealant, e.g. glass, which seals the flange to the header, a portion of the pin above the flange passing through an opening in the header for this purpose.
The pins of the switch device of No. 3,211,875 are affixed between their flanges and their upper ends, which are spun or flanged over, to a thermo-setting phenolic plastic base member.
The connector of No. 3,670,294, has a portion of the pins thereof formed with an X shaped cross section, the arms of which extend from a center rectangular section. The tips of the wings engage the corners of a rectangular cross section opening in an insulator block so as to affix the pins to the block.
The pins of No. 4,753,602 are initially affixed to their housing by providing the pin receiving openings of the housing member with cross sectional configurations compatible with the cross section configurations of the portions of the pins located within the openings. As the lower ends of the pins are inserted into the openings of a printed circuit board, the cross sectional portions move into other passages with larger cross sections so as to be free to move laterally in the housing.
A hollow swaged pin has an enlarged portion which abuts the shoulder of an inner passage of a plastic socket in the device of the aforementioned publication in the IBM Technical Disclosure Bulletin, July 1986, pp 639-640, and thus prevents the pin from being pulled through the bottom of the socket by the disengagement of the plug which mates with the pin.
The metal stem of No. 4,136,259 is held in place in the bore of a ceramic body by projections or teeth formed in the bore which grip the stem.
Affixing pins to a printed circuit board has been done in diverse ways and for diverse reasons. Thus, in No. 2,846,659, a hollow soldering terminal (i.e. a non-pluggable pin) is affixed to a printed circuit board by forming cup shaped expanded portions in the outwardly extending portions of a tubular blank which extends on opposite sides from an opening in a printed circuit board.
A terminal post is affixed to a printed circuit board in No. 2,290,533 by providing a serrated portion of it which when inserted into the opening of the printed circuit board bites into the conductive material in the hole. The serrated portion has a tapered conical cross section which is compatible to a countersunk recess of an opening in the board in which it is disposed and an extended hollow portion which extends through the rest of the opening and outwardly therefrom, the latter being peened over to make contact with the circuitry on the side of the board from which it extends.
In No. 3,093,887, inserts with pins extending therefrom have a preformed flange and a knurled portion below the flange, and the pins become affixed by the knurled section to the board when inserted into the opening of a printed circuit board.
A weldable pin with a pre-formed flange is affixed to a printed circuit board in No. 3,202,755 by inserting the splined lower portion into the opening of the board to cut into its conductive plating and peening over the end of the splined portion.
An interface pin blank is affixed within the opening of a printed circuit board by compressing it at both ends so that it radially expands within the opening in No. 3,484,937.
A length of wire is provided with a cutting edge so that it cuts out a portion of a printed circuit board and extends on both sides of the board where it is subsequently soldered to the concentric lands on both sides of the board and thus is held in place in No. 3,494,029.
A pin blank with a ferrule which extends outwardly on both sides of a printed circuit board from a hole therein is secured to the board by forming outwardly bowed collars on the ends of the ferrule in No. 3,601,750.
In Australian Patent, No. 247,445, a soldering terminal is affixed to an insulating base by forming expanded stops in a wire which passes through the base.
In Canadian Patent, No. 891,180, and the IBM Technical Disclosure Bulletin, Vol. 9, No. 4, September 1966, p 365, the pins are affixed to a printed circuit board by projecting them at high velocity into and/or partially thru the board.
Affixing pins, and in particular pluggable pins, to a ceramic substrate has been a major concern in the prior art because of the frangible and brittle nature of ceramic materials and their tendency to crack or chip especially in the vicinity of the pin holes when subjected to the stresses involved with affixing the pins.
In U.S. Pat. Nos. 3,216,097, 3,257,708, 3,768,134 and the IBM Technical Disclosure Bulletin, Vol. 14, No. 9, February 1972, p 2594, blank pins are fed into the holes of a ceramic substrate and in sequential operational steps a head and a bulge are formed in the pin blank to affix the pin to the substrate. In U.S. Pat. Nos. 3,216 097 and 3,768,134, a flush mounted resilient block centrally is located in a nest formed in a die plate which supports the ceramic substrate. The die plate has peripheral guide holes located around the nest which receive the pin blanks that extend from the aligned holes of the substrate. When the pin blanks are forced into the openings of the substrate a spring biased rubber tipped finger resiliently presses the central portion of the substrate down on the resilient block holding it firmly to prevent fracture.
In U.S. Pat. No. 3,489,879, a pin with a preformed shoulder is inserted into a opening of a ceramic substrate up to the shoulder. After the insertion, a head is formed on the end of the blank using a thermoswaging method which employs pressure and heat, followed by a cooling step, which leaves the portion of the pin between the head and the shoulder in tension and thereby affixing the pin to the ceramic.
In another device, nearly flush pin blanks are inserted into an elongated slot formed in a ceramic substrate and then compressed at its slightly protruding ends so as to expand radially in the slot and become affixed to the ceramic substrate as disclosed in U.S. Pat. No. 3,529,120. Another pin is inserted in the open side of the slot orthogonal to the first mentioned pin with its end abutted and welded to the side of the first pin.
The pin blanks of U.S. Pat. No. 3,735,466 are inserted in the openings of a ceramic substrate and extend into the guide holes or cavities of individual bushings. Next, formation of the pin heads by a ram occurs. The regions surrounding the holes of the ceramic substrate are supported by the end faces of the bushings facing the ceramic substrate, and the bushings in turn are supported on a resilient pad thus reducing cracking in the substrate in the vicinity of the holes during the head forming operation.
Typical electronic circuit packages employing pinned ceramic substrates are described in U.S. Pat. Nos. 4,082,394 and 4,092,697. The pin of U.S. Pat. No. 4,082,394 is illustrated as having a flange and headless, and the pin of U.S. Pat. No. 4,092,697 is illustrated as being headless and flangeless.
The pin blank of U.S. Pat. No. 4,110,904 has a preformed flange which is inserted into an opening of a ceramic substrate up to the flange. Thereafter, a head is formed by a ram in the inserted end of the pin blank.
In U.S. Pat. No. 4,598,470, the ends of pin blanks are inserted into circular apertures of ceramic green sheets. When sintered the apertures shrink to an elliptical cross section and the inserted pins expand to a compatible configuration and results in the affixing of the pin to the sintered substrate.
In IBM Technical Disclosure Bulletin, Vol. 14, No. 1, June 1971, pp 174-175, the ends of pins are inserted into the openings of a pressed unfired ceramic, and the remainder of the pin is inserted in an opening of a graphite mold fixture. A subsequent firing cycle cures the ceramic and the pins assume the shape of the respective openings of the ceramic substrate and mold, which is subsequently removed, leaving the pins affixed to the substrate.
In the impact pinners of U.S. Pat. Nos. 4,415,113 and 4,631,821, the pin blanks are inserted in the openings of a ceramic substrate and impacted simultaneously at both ends to place the blank in a temporary viscoelastic state which causes a resultant metal flow in each pin that penetrates the ceramic particles in the wall of the opening. Upon return to its solid state, the metal flow remains interlocked with the ceramic particles, thus affixing the pin to the substrate.
The pin blanks of IBM Technical Disclosure Bulletin, Vol. 22, No. 8B, January 1980, pp 3649-3650 are inserted in the openings of a ceramic substrate and extend into segmented floating anvils. Next, formation of the pin heads by segmented floating rams occurs. The ceramic substrate is supported on the anvils, and both the anvils and rams are supported on fluid filled bladders. As a result, bending stresses are mitigated during the formation of the pin head.
However, the cracking of ceramic substrates during pinning, i.e. affixing pins to the ceramic substrate, still plagues the industry and with the advent of higher pin counts, greater pin densities, and/or further miniaturization of the pin diameters and sizes, the problem is compounded even further. Part of the problem is that the substrate even when precision made is subject to have some inherent degree of surface irregularity such as warpage and the like which creates stresses in the ceramic during the pinning causing it to crack. While the prior art such as, for example, the cushioning pads of U.S. Pat. Nos. 3,216,097 and 3,215,708, or the individual bushings and resilient pad of U.S. Pat. No. 3,735,466, or the individual rams and anvils and fluid filled bladders of the aforementioned Modlo et al publication, are directed to the relief of the stress during pinning caused by the inherent surface irregularity of the ceramic substrate, they are still inadequate, cumbersome, complex and/or expensive for the needs of today's high density, high pin counts and/or miniaturization requirements.